What this means in plain English: American Elm moves a moderate amount — a 24-inch flatsawn board will grow and shrink about 0.65 inches across its width between a humid summer and a dry winter. For wide panels over 12 inches, lean on quartersawn stock to keep it flat.
How much it moves at common board widths
Find the width of your board on the left. Find your expected moisture swing along the top (8% is typical for a heated/cooled house; 12% is typical outdoors or in a shop without climate control). The number inside the table is how many inches the board will grow and shrink across its width. That’s your slot size.
| Board width | Δ4% MC | Δ6% MC | Δ8% MC | Δ12% MC |
|---|---|---|---|---|
| 6 in | 0.081" | 0.122" | 0.162" | 0.243" |
| 12 in | 0.162" | 0.243" | 0.324" | 0.487" |
| 18 in | 0.243" | 0.365" | 0.487" | 0.730" |
| 24 in | 0.324" | 0.487" | 0.649" | 0.973" |
| 36 in | 0.487" | 0.730" | 0.973" | 1.460" |
How to use it: find your board width in the left column and the expected moisture content change across the top. The cell is the total inches of cross-grain expansion and contraction you should plan for — elongated slots, breadboard clearances, and panel gaps all come from this number.
About American Elm
- Color
- Light to medium brown, often with reddish hue.
- Grain
- Interlocked, coarse uneven texture.
- Workability
- Difficult to split due to interlocked grain, machines moderately well.
- Durability
- Low decay resistance.
- Common uses
- Furniture, boxes, crates, hockey sticks.
- Typical price
- $3-7/bf
- Specific gravity
- 0.50 (oven-dry)
- Modulus of elasticity
- 1,340 × 1,000 psi
The math, explained once
Three numbers multiplied together. That’s it.
width (in) × coefficient × ΔMC (%) = movement (in)
- Width is how wide the board is, measured across the grain.
- Coefficient is the number at the top of this page (tangential 0.00338 for flatsawn, radial 0.00155 for quartersawn).
- ΔMC is how many percentage points the moisture content will change between seasons. Indoor heated spaces: around 8. Shops, garages, or outdoor pieces: 10–14.
These coefficients come from the USDA Forest Products Laboratory and published wood science data. Dead On uses the same numbers on iPhone, iPad, and Apple Watch — your shop math matches your field math.
Calculate American Elm movement in your project
Dead On has this species built in, alongside 29 others — with visual diagrams for dovetails, box joints, mortise & tenon, and more.
Download Dead On — FreeFrequently asked questions about American Elm
How much does American Elm move seasonally?
A 24" wide flatsawn American Elm board will move about 0.65" across the grain with an 8% change in moisture content (typical indoor seasonal swing). The tangential coefficient is 0.00338 per 1% MC change, the radial coefficient is 0.00155.
Is American Elm stable enough for wide tabletops?
American Elm is moderately stable. The tangential-to-radial ratio is 2.18 (lower is more stable; values under 2.0 are ideal for wide panels). For the most stable results, use quartersawn stock or breadboard ends with elongated slots for seasonal movement.
What is American Elm typically used for?
Furniture, boxes, crates, hockey sticks.
Is American Elm a hardwood or softwood?
American Elm is a hardwood. Its Janka hardness rating is 830 lbf and specific gravity is 0.50.
Species with similar movement
Hardwoods with tangential coefficients closest to American Elm’s 0.00338. If your project plan calls for American Elm but availability is tight, these behave most like it through the seasons.